System for optimizing anchoring force

ABSTRACT

Systems for optimizing anchoring force are described herein. In securing tissue folds, over-compression of the tissue directly underlying the anchors is avoided by utilizing tissue anchors having expandable arms configured to minimize contact area between the anchor and tissue. When the anchor is in its expanded configuration, a load is applied to the anchor until it is optimally configured to accommodate a range of deflections while the anchor itself exerts a substantially constant force against the tissue. Various devices, e.g., stops, spring members, fuses, strain gauges, etc., can be used to indicate when the anchor has been deflected to a predetermined level within the optimal range. Moreover, other factors to affect the anchor characteristics include, e.g., varying the number of arms or struts of the anchor, positioning of the arms, configuration of the arms, the length of the collars, etc.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is related to co-pending U.S. Pat. App. Ser. No.10/______filed on the same day (Attorney docket no. 021496-001800US),which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention. The present invention relates to apparatusand methods for optimizing the force for securing anchors againsttissue. More particularly, the present invention relates to apparatusand methods for optimizing the force for loading basket-type anchorswithin or against tissue within a body.

Morbid obesity is a serious medical condition pervasive in the UnitedStates and other countries. Its complications include hypertension,diabetes, coronary artery disease, stroke, congestive heart failure,multiple orthopedic problems and pulmonary insufficiency with markedlydecreased life expectancy.

A number of surgical techniques have been developed to treat morbidobesity, e.g., bypassing an absorptive surface of the small intestine,or reducing the stomach size. However, many conventional surgicalprocedures may present numerous life-threatening post-operativecomplications, and may cause atypical diarrhea, electrolytic imbalance,unpredictable weight loss and reflux of nutritious chyme proximal to thesite of the anastomosis.

Furthermore, the sutures or staples that are often used in thesesurgical procedures typically require extensive training by theclinician to achieve competent use, and may concentrate significantforce over a small surface area of the tissue, thereby potentiallycausing the suture or staple to tear through the tissue. Moreover, thetissue underlying the suture or staple may be subject to becomingover-compressed to the point of becoming subject to necrosis. Many ofthe surgical procedures require regions of tissue within the body to beapproximated towards one another and reliably secured without necrosingthe approximated tissue. The gastrointestinal lumen includes four tissuelayers, wherein the mucosa layer is the inner-most tissue layer followedby connective tissue, the muscularis layer and the serosa layer.

One problem with conventional gastrointestinal reduction systems is thatthe anchors (or staples) should engage at least the muscularis tissuelayer in order to provide a proper foundation. In other words, themucosa and connective tissue layers typically are not strong enough tosustain the tensile loads imposed by normal movement of the stomach wallduring ingestion and processing of food. In particular, these layerstend to stretch elastically rather than firmly hold the anchors (orstaples) in position, and accordingly, the more rigid muscularis and/orserosa layer should ideally be engaged. This problem of capturing themuscularis or serosa layers becomes particularly acute where it isdesired to place an anchor or other apparatus transesophageally ratherthan intraoperatively, since care must be taken in piercing the toughstomach wall not to inadvertently puncture adjacent tissue or organs.Thus, an anchor is desirably non-traumatic to the surrounding tissue.Moreover, the anchor is also desirably strong enough to withstand themovement of the tissue.

One conventional method for securing anchors within a body lumen to thetissue is to utilize sewing devices to suture the stomach wall intofolds. This procedure typically involves advancing a sewing instrumentthrough the working channel of an endoscope and into the stomach andagainst the stomach wall tissue. The contacted tissue is then typicallydrawn into the sewing instrument where one or more sutures or tags areimplanted to hold the suctioned tissue in a folded condition known as aplication. Another method involves manually creating sutures forsecuring the plication.

One of the problems associated with these types of procedures is thetime and number of intubations needed to perform the various proceduresendoscopically. Another problem is the time required to complete aplication from the surrounding tissue with the body lumen. In the periodof time that a patient is anesthetized, procedures such as for thetreatment of morbid obesity or for GERD must be performed to completion.Accordingly, the placement and securement of the tissue plication shouldideally be relatively quick and performed with a minimal level ofconfidence.

Another problem with conventional methods involves ensuring that thestaple, knotted suture, or clip is secured tightly against the tissueand that the newly created plication will not relax under any slackwhich may be created by slipping staples, knots, or clips. Otherconventional tissue securement devices such as suture anchors, twistties, crimps, etc. are also often used to prevent sutures from slippingthrough tissue. However, many of these types of devices are typicallylarge and unsuitable for low-profile delivery through the body, e.g.,transesophageally. Moreover, these methods do not allow the surgeon togauge the amount of force being applied to or against the tissue by thesutures, staple, clip, etc. Thus, over-tightening of the tissue anchoragainst the underlying tissue surface may be problematic.

Moreover, when grasping or clamping onto or upon the layers of tissuewith conventional anchors, sutures, staples, clips, etc., many of thesedevices are configured to be placed only after the tissue has beenplicated and not during the actual plication procedure.

BRIEF SUMMARY OF THE INVENTION

In securing the tissue folds or anchoring to or from these tissue foldsor plications, over-compression of the tissue directly underlying thetissue anchors is preferably avoided. Over-compression of the underlyingtissue may occur if the anchor compresses the tissue to such a degreethat tissue necrosis or cutting of the underlying muscularis or serosaltissue by the anchor occurs. Accordingly, a tissue anchor is preferablyconfigured to maintain or secure a tissue plication yet still allow foradequate blood flow to occur within the tissue underlying the anchor. Assuch, the tissue anchor is preferably configured to accommodate a rangeof deflections due to various movements of the tissue due to, e.g.,peristalsis, patient movement, weight of the gastrointestinal organitself, etc., while maintaining or exerting a substantially constantforce against the tissue.

A particular type of anchor which may be utilized is a reconfigurable“basket”-type anchor generally having a number of configurable struts orlegs extending between at least two collars or bushing members. Thisanchor may have a low-profile delivery configuration and a radiallyexpanded anchoring configuration. When expanded, each arm of the anchormay be separated from one another by a spacing or opening. The spacingis preferably created to minimize the contact area between the anchorbody and the underlying tissue surface to allow for greater blood flowin the tissue and to inhibit necrosis of the tissue.

The anchor may be made from various materials, e.g., spring stainlesssteel, plastics such as polyurethane, nylon, etc., but is preferablymade from a shape memory or superelastic alloy, e.g., Nitinol. Theanchor may thus be shaped and heat-set such that it self-forms orautomatically configures itself from the delivery configuration to theexpanded configuration upon release of a constraining force, e.g., whenthe anchor is ejected from its delivery needle or catheter. Sutures mayconnect a proximal anchor to a distal anchor through the tissue fold tosecure the plication.

When the anchor has been configured into its expanded configuration, aload or force may be applied to the anchor until the anchor has beenoptimally configured to accommodate a range of deflections while theanchor itself maintains or exerts a substantially constant force againstthe tissue. Anchor deflection may occur, e.g., when the proximal anddistal collars of an anchor have been advanced or urged towards oneanother such that the arms or struts extending therebetween are at leastpartially deflected. Moreover, anchor deflection may be due to variousmovements of the tissue attributable to, e.g., peristalsis, patientmovement, weight of the gastrointestinal organ itself, etc.

Knowing the anchor deflection-to-exerted force characteristics for agiven anchor, one may load an anchor with a tension or compression forcesuch that subsequent deflections of the underlying tissue being anchoredoccur within specified ranges, such as the optimal range. For instance,an anchor may be pre-loaded such that tissue fluctuations or movementsoccur within the optimal window or range where the force exerted by theanchor remains relatively constant over a range of deflections. This inturn may ensure that the underlying tissue is not subject toover-compression by the anchors.

One method for limiting the loading or pre-load force upon an anchor mayinvolve including a post or stop in the anchor body which limits theproximal deflection of the distal collar and thus preventsover-compression of the anchor against the tissue. Another variation mayutilize friction-producing regions within the anchor delivery catheter.As the anchor is tensioned, various regions may produce frictionalforces which vary in accordance to the degree of anchor deflection. Achange in the detected frictional force may thus be utilized to indicatethat anchor has been configured within an optimal range of deflections.

Another variation may include the use of a spring member having a knownspring constant or fuse-like member which are set to break or fail atpredetermined levels of detected force to detect the amount ofdeflection an anchor has undergone. Alternatively, measurement ofmaterial deformation via strain gauges may also be utilized to determinethe amount of deflection. The anchor tensioning assembly may thus beconfigured to indicate when the anchor has been deflected to apredetermined level, when the anchor has been deflected within theoptimal range.

Yet another variation may include configuring the proximal collar of theanchor to prevent the passage of stop member contained within theanchor. thus, the length of suture extending from the stop member to theattachment point within the anchor may be of a predetermined length suchthat when the stop member is seated against the proximal collar, thesuture length may compress the anchor into a predetermined deflectionlevel. This deflection level may be preset to configure the anchor toany desired configuration, as described above.

The anchors may be tensioned through various methods. One particularmethod may include tensioning the anchors via an elongate rigid orflexible shaft having a hollow lumen. A tensioning mechanism, which isconfigured to receive the anchors and grasp a tensioning suture, may bepositioned near or at the distal end of the elongate shaft. After theanchor or anchors have been desirably tensioned, the shaft may simply beremoved from the body.

Various other factors of the tissue anchors may be modified to affectthe tensioning and loading characteristics when deflecting the anchors.Moreover, some of the factors may also affect the interaction of theanchor with respect to the tissue in ensuring that the tissue is notover-compressed and that adequate blood flow may occur within the tissuedirectly beneath the anchor. Some of the factors may include, e.g.,varying the number of arms or struts of the anchor, positioning of thearms, configuration of the arms, the length of the collars, etc.

Moreover, exposed portions of the anchor may be optionally coated orcovered with a material to protect against exposure to foreignmaterials, e.g., food or other object which may be ingested by thepatient, other surgical tools, etc. Accordingly, a biocompatible coatingor covering may be placed over the entire length of the anchor arms oronly along the portions of the arms not against the tissue.Alternatively, a mesh or skirt-like covering may be placed over theexposed portion of the anchor or the entire anchor itself may be coveredwith a distensible or expandable covering or mesh.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B show perspective views of an example of a basket-typeanchor in a delivery configuration and an expanded configuration,respectively.

FIG. 2A shows a cross-sectional side view of one variation fordelivering a basket anchor through a needle for anchoring to a fold oftissue.

FIG. 2B shows a cross-sectional side view of examples of how basketanchors may be utilized in anchoring tissue plications.

FIGS. 3A and 3B show a graph of initial displacement or deflectionversus exerted force and an example of a tissue anchor correspondinglydisplaced, respectively.

FIGS. 4A and 4B show the graph illustrating an optimal range of anchordeflection where the exerted force by the anchor remains substantiallyconstant and the correspondingly compressed anchor, respectively.

FIGS. 5A and 5B show the graph illustrating the rising force for anover-compressed anchor and the correspondingly compressed anchor,respectively.

FIGS. 6A and 6B show cross-sectional side views of an anchor having acenter post extending within the anchor for limiting the compression ofthe anchor.

FIGS. 7A and 7B show cross-sectional side views of one variation of ananchor tensioning or loading mechanism utilizing different frictionalcoefficients to indicate the load placed upon the anchor.

FIGS. 8A and 8B show the corresponding frictional force generatedutilizing the device of FIGS. 7A and 7B, respectively.

FIG. 9 shows a partial cross-sectional view of another variation of ananchor loading mechanism which utilizes a spring member having a knownspring constant.

FIG. 10 shows a partial cross-sectional view of another variation of ananchor loading mechanism utilizing a strain gauge for measuring thestrain, and the resultant load, exerted upon the anchor.

FIG. 11 shows a cross-sectional view of another variation of an anchorloading mechanism which utilizes a stop for limiting the anchorcompression to a predetermined limit.

FIGS. 12A and 12B show partial cross-sectional views of anothervariation of an anchor loading mechanism utilizing a fuse-like deviceset to break or release upon reaching a predetermined load.

FIGS. 13A and 13B show side views of various notched fuse-members whichmay be utilized with the variation of FIGS. 12A and 12B.

FIG. 14A shows a partial cross-sectional side view of a device which maybe used to apply the load upon the loading mechanism.

FIG. 14B shows a perspective view of an alternative loading mechanism.

FIG. 14C shows a side view of an assembly in which the loading mechanismmay be placed for applying the load upon the anchors.

FIGS. 15A and 15B show side and edge views, respectively, of onevariation of a basket anchor in a flattened and splayed view

FIG. 15C shows a perspective view of the anchor of FIGS. 15A and 15B inits delivery configuration.

FIGS. 16A and 16B show side and edge views, respectively, of anothervariation of a basket anchor in a flattened and splayed view

FIG. 16C shows a perspective view of the anchor of FIGS. 16A and 16B inits delivery configuration.

FIGS. 17A to 17J show cross-sectional end views of the proximal (I),middle (II), and distal (III) portions of a single anchor strut or armshowing some of the various shapes that the anchor strut or arm may beconfigured.

FIGS. 18A to 18F show examples of end views of anchors having anincreasing number of struts or arms.

FIGS. 19A to 19F show examples of side views of anchors having variousstrut or arm configurations.

FIGS. 20A and 20B show side views of anchors having variousconfigurations affected by the heights of the anchor collars.

FIG. 21A shows a perspective view of an anchor in an expandedconfiguration having a protective coating or covering over at least aportion of the struts or arms.

FIG. 21B shows a perspective view of another anchor having a protectivecovering or mesh over at least a portion of the anchor facing away fromthe tissue surface.

FIG. 21C shows a perspective view of another anchor having a protectivecovering or mesh over the entire anchor body.

DETAILED DESCRIPTION OF THE INVENTION

Generally, in creating and securing a plication within a body lumen of apatient, various methods and devices may be implemented. The anchoringand securement devices may be delivered and positioned via an endoscopicapparatus that engages a tissue wall of the gastrointestinal lumen,creates one or more tissue folds, and disposes one or more of theanchors through the tissue fold(s).

In securing the tissue folds or anchoring to or from these tissue foldsor plications, over-compression of the tissue directly underlying thetissue anchors is preferably avoided. Over-compression of the underlyingtissue may occur if the anchor compresses the tissue to such a degreethat tissue necrosis or cutting of the underlying muscularis or serosaltissue by the anchor occurs. The anchor preferably exerts a force, e.g.,about 0.1-0.5 lbs, sufficient to maintain or secure a tissue plicationyet still allows for adequate blood flow to occur within the tissueunderlying the anchor. Accordingly, the tissue anchor is preferablyconfigured to accommodate a range of deflections due to variousmovements of the tissue due to, e.g., peristalsis, patient movement,weight of the gastrointestinal organ itself, etc., while maintaining orexerting a substantially constant force against the tissue.

Formation of a tissue fold may be accomplished using at least two tissuecontact areas that are separated by a linear or curvilinear distance,wherein the separation distance between the tissue contact pointsaffects the length and/or depth of the fold. In operation, a tissuegrabbing assembly engages or grasps the tissue wall in its normal state(i.e., non-folded and substantially flat), thus providing a first tissuecontact area. The first tissue contact area then is moved to a positionproximal of a second tissue contact area to form the tissue fold. Thetissue anchor assembly then may be extended across the tissue fold atthe second tissue contact area. Optionally, a third tissue contact pointmay be established such that, upon formation of the tissue fold, thesecond and third tissue contact areas are disposed on opposing sides ofthe tissue fold, thereby providing backside stabilization duringextension of the anchor assembly across the tissue fold from the secondtissue contact area.

The first tissue contact area may be utilized to engage and then stretchor rotate the tissue wall over the second tissue contact area to formthe tissue fold. The tissue fold may then be articulated to a positionwhere a portion of the tissue fold overlies the second tissue contactarea at an orientation that is substantially normal to the tissue fold.A tissue anchor may then be delivered across the tissue fold at or nearthe second tissue contact area. One apparatus which is particularlysuited to deliver the anchoring and securement devices described hereinmay be seen in further detail in co-pending U.S. Pat. App. Ser. No.10/735,030, filed Dec. 12, 2003, which is incorporated herein byreference in its entirety.

Various tissue anchors may be utilized for securing the tissueplications within the lumen. For instance, examples of tissue anchorswhich may be utilized are disclosed in co-pending U.S. Pat. App. Ser.No. 10/612,170, filed Jul. 1, 2003, which is incorporated herein byreference in its entirety. Moreover, a single type of anchor may be usedexclusively in an anchor assembly; alternatively, a combination ofdifferent anchor types may be used in an anchor assembly. One particulartype of anchor described herein is a reconfigurable “basket”-typeanchor, which may generally comprise a number of configurable struts orlegs extending between at least two collars or bushing members.

As described below, a system for loading an anchor for placement againsta tissue surface may generally comprise an anchor body having a deliveryconfiguration and an expanded configuration adapted for placementagainst the tissue surface, and a loading mechanism in communicationwith the anchor body, wherein the loading mechanism is adapted toindicate a loading condition upon the anchor body.

One particular illustrative basket anchor is shown in the perspectiveviews of FIGS. 1A and 1B. FIG. 1A shows deformable basket anchor 10 in alow-profile delivery configuration having proximal collar or bushing 14and distal collar or bushing 16 with a plurality of struts or arms 12extending between collars 14, 16. Each arm 12 may be separated from oneanother by spacing or opening 20. Moreover, each arm 12 may be alignedparallel with one another although this is not necessary. Anchor 10 maydefine lumen 18 through the length of anchor 10 to allow for the passageof one or more sutures therethrough.

FIG. 1B shows a perspective view of anchor 10 of FIG. 1A in an anchoringor expanded configuration 10′. In such a configuration, proximal collar14 and distal collar 16 are advanced towards one another such that themiddle section 22 of arms 12 extend radially outwardly. Anchor 10′ maybe made from various materials, e.g., spring stainless steel, but ispreferably made from a shape memory or superelastic alloy, e.g.,nitinol. The anchor may thus be shaped and heat-set such that itself-forms or automatically configures itself from the deliveryconfiguration 10 to the expanded configuration 10′ upon release of aconstraining force, e.g., when the anchor is ejected from its deliveryneedle or catheter, as described further below. Alternatively, theanchor may be configured to self-form into its expanded configuration10′ upon the application of some activation energy to the anchor, e.g.,electrical energy, heat from the surrounding tissue, etc.

Upon expanding, the arms 12 of anchor 10′ may extend radially outwardlysuch that spacing or opening 20′ is defined between adjacent arms 12.The spacing 20′ is preferably created to minimize the contact areabetween the anchor body and the underlying tissue surface to allow forgreater blood flow in the tissue and to inhibit necrosis of the tissue.

When anchor 10′ contacts the tissue surface, proximal collar 14 andproximal section 24 of arm 12 lay against the tissue while distalsection 26 of arm 12 extends away from the tissue surface. Althoughseven arms 12 are shown in this example, the number of arms is notintended to be limiting and may be varied, as described in furtherdetail below. Moreover, the configurations of proximal 24, distal 26,and middle section 22 of arms 12 may also be varied and is alsodescribed in further detail below.

Deploying the anchors against, into, or through the tissue may beaccomplished in a number of ways. One example is shown in FIG. 2A, whichshows a cross-section of an anchor delivery system 30 in proximity totissue fold F. Tissue fold F may comprise a plication of tissue createdusing any number of tissue plication devices. Examples of such deviceswhich may be utilized are described in further detail in U.S. Pat. App.Ser. No. 10/735,030, filed Dec. 12, 2003. Tissue fold F may be disposedwithin a gastrointestinal lumen, such as the stomach, where tissue wallW may define the outer or serosal layer of the stomach. The anchordelivery assembly may generally comprise launch tube 32 and needle 40slidingly disposed within the launch tube lumen. Needle 48 may generallybe configured as a hollow needle having a tapered or sharpened distalend to facilitate its travel into and/or through the tissue.

Delivery push tube or catheter 34 may be disposed within launch tube 32proximally of basket anchor 10, which is shown in a compressed deliveryconfiguration with a relatively low profile when disposed within needlelumen 42 of needle 40. A single basket anchor 10 is shown disposedwithin needle 40 only for illustrative purposes and is not intended tobe limited by the number of basket anchors; rather, any number of basketanchors may be disposed within needle lumen 42 as practicable dependingupon the desired procedure and anchoring results.

Once launch tube 32 has been desirably positioned with respect to tissuefold F, needle 40 may be urged or pushed into or through tissue fold Fvia needle pushrod or member 44 from its proximal end. As shown in FIG.2B, basket anchor 56 has been urged or ejected from needle 40 and isshown in its radially expanded profile for placement against the tissuesurface. In such a case, a terminal end of suture 66 may be anchoredwithin the distal collar of anchor 64 and routed through tissue fold Fand through, or at least partially through, proximal anchor 56, wheresuture 38 may be cinched or locked proximally of, within, or at proximalanchor 56 via any number of cinching or locking mechanisms 68. Proximalanchor 56 is also shown in a radially expanded profile contacting tissuefold F along tissue contact region 54. Locking or cinching of suture 38proximally of proximal anchor 56 enables the adequate securement oftissue fold F.

A single suture or flexible element 38 (or multiple suture elements) mayconnect proximal anchor 56 and distal anchor 64 to one another throughtissue fold F in the case of a single tissue fold F. If additionaltissue folds are plicated for securement, distal anchor 46 may bedisposed distally of at least one additional tissue fold F′ whileproximal anchor 56 may be disposed proximally of tissue fold F. Asabove, suture 38 may be similarly affixed within distal anchor 46 androuted through proximal anchor 56, where suture 38 may be cinched orlocked via cinching or locking mechanism 68, as necessary. Lockingmechanism 68 may be further configured to apply a locking force upon thesuture 38 such that the anchors located upon both sides of tissue fold F(or tissue folds F and F′) may be advanced towards one another whilecinching the tissue plication(s). Suture or flexible element 38 maycomprise various materials such as monofilament, multifilament, or anyother conventional suture material, elastic or elastomeric materials,e.g., rubber, etc.

If tissue folds F and F′ are to be positioned into apposition with oneanother, distal anchor 46 and proximal anchor 56 may be approximatedtowards one another. Proximal anchor 56 is preferably configured toallow suture 38 to pass freely therethrough during the anchorapproximation. However, proximal anchor 56 is also preferably configuredto prevent or inhibit the reverse translation of suture 38 throughproximal anchor 56 by enabling uni-directional travel of anchor 56 oversuture 38. This cinching feature thereby allows for the automatedlocking of anchors 46, 56 relative to one another during anchorapproximation. Aspects of anchor positioning relative to tissue andvarious examples of cinching or locking mechanisms may be seen infurther detail in U.S. Pat. App. Ser. Nos. 10/840,950 filed 05/07/2004(Attorney Docket No. 021496-000900 US); 10/841,245 filed 05/07/2004(Attorney Docket No. 021496-001000 US); 10/840,951 filed 05/07/2004(Attorney Docket No. 021496-001100 US); and 10/841,411 filed 05/07/2004(Attorney Docket No. 021496-001200 US), all of which were filed May 7,2004 and each of which is incorporated herein by reference in itsentirety.

The anchors, as described above, may be seen in FIG. 2B to each haveproximal collars 48, 58 and respective distal collars 50, 60 with strutsor arms 52, 62 extending therebetween. As described above, the basketanchors are preferably reconfigurable from a low profile deliveryconfiguration to a radially expanded deployment configuration in which anumber of struts, arms, or mesh elements may radially extend oncereleased from launch tube 32 or needle 40. Materials having shape memoryor superelastic characteristics or which are biased to reconfigure whenunconstrained are preferably used, e.g., spring stainless steels, Ni-Tialloys such as Nitinol, etc.

The basket anchors are illustrated as having a number of reconfigurablestruts or arm members extending between a distal collar and proximalcollar; however, this is intended only to be illustrative and suitablebasket anchors are not intended to be limited to baskets only havingstruts or arms, as will be described in further detail below. Examplesof suitable anchors are further described in detail in the referenceswhich have been incorporated by reference above as well as in U.S. Pat.App. Ser. No. 10/612,170 filed Jul. 1, 2003, which is also incorporatedherein by reference in its entirety.

As mentioned above, the anchor preferably exerts a force sufficient tomaintain or secure a tissue plication yet still allows for adequateblood flow to occur within the tissue underlying the anchor. When theanchor has been configured into its expanded configuration, a load orforce may be applied to the anchor until the anchor has been optimallyconfigured to accommodate a range of deflections while the anchor itselfmaintains or exerts a substantially constant force against the tissue.Anchor deflection may occur, e.g., when the proximal and distal collarsof an anchor have been advanced or urged towards one another such thatthe arms or struts extending therebetween are at least partiallydeflected. Moreover, anchor deflection may be due to various movementsof the tissue attributable to, e.g., peristalsis, patient movement,weight of the gastrointestinal organ itself, etc.

FIGS. 3A, 4A, and 5A illustrate an example of how the progressivedeflection of an anchor may result in a substantially constant forceexerted by the anchor itself. As shown in the graph 70 of FIG. 3A, anamount of anchor deflection, x, is plotted against the resulting force,F, exerted by the anchor. FIG. 3B shows an illustrative profile of anexemplary anchor; proximal collar 14, distal collar 16, and struts 12are shown for reference. With proximal collar 14 stationary relative tothe anchor, distal collar 16 may be urged initially at some distance, x.The anchor may thus be configured into an initial deflectedconfiguration 72, as shown in FIG. 3B. The deflection may be induced viaa suture or flexible member urging the collars towards one another,e.g., during tissue plication formation or securement.

FIG. 3A shows the corresponding increase in force 78 over the initialloading of the anchor through deflection, x. As the deflection of theanchor is increased, the anchor may be configured into a configuration72′, as shown in FIG. 4B, where the increasing force exerted by theanchor passes an inflection point 74 and enters an “optimal” window orrange 80 in which the exerted force remains relatively constant over arange of deflections, as shown by the loading graph 70′ in FIG. 4A.Within this range 80 of deflections, the amount of force exerted by theanchor may be substantially constant, i.e., relatively constant orincreasing at a rate lower than the rate of initial loading 78 or rateof “over” loading 82 the anchor, as shown below.

At the upper portion of range 80, the force exerted by the anchor maybegin to increase relative to the deflection, as indicated by loadingcurve 82 beyond inflection point 76 shown in the loading graph 70″ ofFIG. 5A. FIG. 5B shows the corresponding over-loaded anchorconfiguration 72″ where the anchor may be seen as having been deflectedbeyond the configuration shown in FIG. 4B. The force representing theover loading of the anchor may increase steadily until the anchor isforced into a configuration where proximal 14 and distal 16 collars havebeen urged towards one another to the point where they contact oneanother.

Knowing the anchor deflection-to-exerted force characteristics for agiven anchor, one may load an anchor with a tension or compression forcesuch that subsequent deflections of the underlying tissue being anchoredoccur within specified ranges, such as the optimal range. For instance,an anchor may be pre-loaded such that tissue fluctuations or movementsoccur within the optimal window or range where the force exerted by theanchor remains relatively constant over a range of deflections. This inturn may ensure that the underlying tissue is not subject toover-compression by the anchors.

One method for limiting the loading or pre-load force upon an anchor mayinvolve including a post or stop 98 in the anchor body, as shown in theanchor variation 90 of FIG. 6A, which shows a partial cross-sectionalview of the anchor. Post or stop 98 may be integrally formed withproximal collar 94 and extend distally between struts 92. Alternatively,post 98 may also be fabricated separately and attached through one of anumber of mechanical methods to proximal collar 94, e.g., adhesives,threading, interference fitted, etc. Post 98 may define a lumen to allowsuture 38 to pass through the anchor 90. The anchor 90 may be loaded viasuture 38 until the anchor 90 is configured to fall within the optimalwindow or range. As the underlying tissue moves, the anchor may bedeflected accordingly; however, if the anchor is subjected to largedeflections by the tissue, post 98 may prevent distal collar 96 of theanchor from over-compressing the anchor, as shown in the compressedconfiguration 90′ of FIG. 6B.

Another variation which may be utilized to limit the loading of theanchor during anchor placement and tensioning against the tissue isshown in the partial cross-sectional views of FIGS. 7A and 7B.Tensioning assembly 100 may be seen proximally of anchor proximal collar14 contained within the delivery push tube or catheter 102. An elongatemember 104, e.g., a tubular member, may extend through catheter 102 anddefine a specified region 108 having a known coefficient of frictionnear or at the distal end of elongate member 104. Frictional region 108may be an area of the elongate member 104 having a separate material ofknown frictional coefficient coated or adhered thereon. Alternatively,the frictional region 108 may be integral with elongate member 104 andmay simply be abraded or roughened to alter the frictional coefficientof region 108.

Suture 38 may be attached at attachment point 106 to the distal end ofelongate member 104 and may further extend into the anchor. As elongatemember 104 is slid proximally through catheter 102 to impart a tensionor load upon the anchor via suture 38, member 104 may pass through atleast one or more regions which are in intimate contact around member104. The regions in contact with member 104 may comprise at least afirst frictional area 110 having a known first frictional coefficient.As elongate member 104 is withdrawn proximally in the direction oftravel 118, frictional region 108 may slide against first frictionalarea 110 and generate a first frictional force I, as indicated by plot120 on the graph of FIG. 8A. The generated first frictional force I maybe detected through any number of various devices and may be used toindicate to the operator that anchor is being loaded.

As elongate member 104 is withdrawn further proximally, frictionalregion 108 may be withdrawn proximally of first frictional area 110 andagainst second frictional area 112, which may also have a known secondfrictional coefficient different from the first frictional coefficientof the first frictional area 110, as shown in FIG. 7B. A length of firstfrictional area 110 may accordingly be configured to correspond to thelength of suture needed to load the anchor into its optimalconfiguration. As elongate member 104 slides against second frictionalarea 112, a second frictional force II may be generated which may beless than the first frictional force. FIG. 8B shows the drop in thegenerated frictional force as indicated by plot 122. This change in thedetected force may thus be utilized to indicate to the operator thatanchor has been configured within an optimal range of deflections. Oncethe anchor has been optimally configured, the suture may be securedrelative to the anchor using any number of the cinching and/or lockingmethods as described in U.S. Pat. App. Ser. Nos. 10/840, 950 filed05/07/2004 (Attorney Docket No. 021496-000900 US); 10/841,245 filed05/07/2004 (Attorney Docket No. 021496-001000 US); 10/840,951, filed05/07/2004 (Attorney Docket No. 021496-001100 US); and 10/841, 411 filed05/07/2004 (Attorney Docket No. 021496-001200 US), which have beenincorporated by reference above.

To prevent elongate member 104 from being over-withdrawn proximally andfrom over-compressing the anchor, protrusions 114 may project fromelongate member 104 and corresponding stops 116 may project from withincatheter 102. Protrusions 114 and the corresponding stops 116 mayaccordingly be configured to prevent the further withdrawal of elongatemember 104 from catheter 102. Moreover, although first 110 and second112 frictional areas are shown in this example, a single frictional areaor additional areas may be utilized, each having a different coefficientof friction. Furthermore, first 110 and second 112 frictional areas maybe fabricated from different materials or they may be made from the sameor similar material as catheter 102 and simply coated or covered withthe various materials. For instance, first frictional area 110 may befabricated from a material such as PEBAX®, while second frictional area112 may be fabricated from a material such as HDPE. Alternatively,rather than utilizing a coating or covering, first 110 and second 112frictional areas may be textured or abraded to create surfaces havingdiffering frictional coefficients. The types of materials utilized orthe types of surface textures created or even the number of differentfrictional areas are not intended to be limiting but are merelypresented as possible variations. So long as a detectable change in thegenerated frictional force between elongate member 104 and thesurrounding frictional region is created, any number of materials orregions may be utilized.

FIG. 9 shows another anchor tensioning variation in assembly 130. Asshown, the tensioning assembly may be contained within delivery pushtube or catheter 132. An elongate pull member 134, which may bemanipulated via its proximal end by the user, may be connected to atensioning block or member 136 via spring member 138. Pull member 134and tensioning block or member 136 may generally be formed from avariety of biocompatible metals, e.g., stainless steel, Nitinol, etc.,or plastics provided that the material is rigid relative to springmember 138 and suture 140 and will not affect the measurement of thelinear deformation of spring member 138. Spring member 138 may generallycomprise a linear spring element having a known spring constant. Suture140 may be attached to a distal end of block 136 and further routed intoor through distally located the tissue anchor.

During use in loading the tissue anchor, pull member 134 may bewithdrawn proximally by its proximal end. As it is withdrawn, the forcerequired to withdraw member 134 may be measured. With the springconstant and the measured force, the amount of linear deflection may becalculated to determine the amount of deflection the anchor hasundergone. Alternatively, suture 140 may be marked uniformly at knowndistances with markings or gradations 142. As the pull member 134 iswithdrawn, the length of suture 140 withdrawn into catheter 132 may bemeasured visually using, e.g., a video endoscope, by counting the numberof gradations 142 passing into catheter 132.

Knowing the linear distance and the spring constant, the anchordeflection may be calculated. Thus, measurement of either the forcerequired to withdraw member 134 or the linear distance traveled bysuture 140 may be utilized to determine the anchor deflection. With theknown deflection, the assembly may be configured to indicate when theanchor has been deflected to a predetermined level, e.g., when theanchor has been deflected within the optimal range.

Another alternative of an anchor tensioning assembly is shown in thepartial cross-sectional view of FIG. 10. Assembly 150 may generallycomprise an elongate pull member 152 connected to tensioning block ormember 154. Pull member 152 and tensioning block 154 may be fabricatedfrom the same or similar materials as described above. A third element156 having a known length which is less rigid than pull member 152 ortensioning block 154 may connect the two. This element 156 may havestrain gauge 158 attached thereto for measuring the strain of theelement 156 as pull member 152 is withdrawn proximally. The signalsdetected from the strain gauge 158 may be transmitted via wires 160 to aprocessor and/or display 162 located externally of the patient to recordand process the strain information. With the known original length ofelement 156 and the measured strain, the length of linear deflection ofthe attached anchor may be calculated. With this information, the anchordeflection may be determined and the assembly 150 may be configured toindicate when the anchor has been deflected to a predetermined level toensure optimal loading of the anchor.

Yet another alternative is shown in the partial cross-sectional view ofFIG. 11. In this variation, assembly 170 may simply comprise an anchorhaving a stepped proximal collar 172 to define a step or detent 174which prevents the passage of stop member 176 contained within theanchor. The length of suture 38 extending from stop member 176 to theattachment point within the anchor may be of a predetermined length suchthat when stop member 176 is seated against proximal collar 172, thesuture length may compress the anchor into a predetermined deflectionlevel. This deflection level may be preset to configure the anchor toany desired configuration, as described above.

Yet another variation is shown in the partial cross-sectional views ofFIGS. 12A and 12B. Assembly 180 may generally comprise elongate pullmember 152 and tensioning block or member 154, as above. However, a fusematerial 182, i.e., a length of material having a preset or knownfailure or break strength, may be used to join pull member 152 andtensioning block 154. This fuse 182 may generally comprise a variety ofmaterials, e.g., silk, stainless steel, etc., provided that the failurestrength of fuse 182 is less than the force necessary for causingnecrosis of the tissue to be anchored. For instance, a fuse 182 may beconfigured to break at a pressure of, e.g., 2 psi.

In operation, as elongate pull member 152 is withdrawn proximally,tensioning block 154 may be withdrawn as it is pulled by fuse 182. Asthe anchor becomes compressed and the force on fuse 182 increases, oncethe force reaches the pre-set limit, the fuse 182 may break, as shown inFIG. 12B, thereby preventing further compression of the anchor andlimiting the force applied onto the tissue.

Fuse 182 may be comprised from various materials. Optionally, the fusemay be altered to modify its break strength, e.g., by including multiplenotches 192, 194, as seen in fuse variation 190 of FIG. 13A to create anecked-down region. Alternatively, a single notch 198 may be utilized,as seen in fuse variation 196. The notches may be defined on the fuse toalter the break strength or to ensure the breakage or failure of thefuse.

When tensioning the anchors using any of the devices or methodsdescribed herein, various mechanisms may be used to apply the tensioningforce on the suture. One mechanism is shown in the partialcross-sectional view of FIG. 14A, which shows a tensioning assembly 200positioned within catheter 132. The assembly may generally comprisetensioning mechanism 202, which may have an anchor interface member 206and a tensioning interface member 208 configured to slide relative toone another within catheter 132. Anchor interface member 206 may defineanchor collar channel 204 configured to receive and temporarily hold theproximal collar 14 of an anchor to be loaded.

Tensioning interface member 208 may be configured to slide relative toanchor interface member 206 via a slidable connection 210. Tensioningmember 208 may also comprise suture coupler 212 and hook 214 for holdingterminal end 216 of suture 38 during a tensioning procedure. Tensioningmember 208 and anchor member 206 may be urged towards one another viasome biased member, e.g., spring member 218, having a known springconstant. In use, when a tissue anchor is ready to be loaded, theproximal collar 14 may be held within anchor collar channel 204 and withterminal end 216 of suture 38 retained by hook 214, tensioning member208 may be withdrawn proximally relative to anchor member 206 until thedesired tensioning level is reached. Other variations utilizing, e.g., astrain gauge, for measuring the tension applied or utilizing, e.g,graspers, rather than a hook may be utilized to desirably tension thetissue anchors.

FIG. 14B shows a perspective view of an alternative tensioning assembly201 which may be used to apply the load upon the anchor. This assembly201 may be utilized in conjunction with any of the tension measuringapparatus described herein. As shown, anchor 10′ may be positioned atthe distal end of base 205 with suture 38 extending proximally whilebeing tensioned via suture coupler 212, as in assembly 200 describedabove. Graspers 203, which may be articulated to open or close, may beused to hold suture terminal end 216 while tensioning anchor 10′. Base205 may be configured to extend longitudinally, as above, or suturecoupler 212 may be configured to slide proximally to tension the anchor10′.

FIG. 14C shows a device which may be used by the surgeon or operatoroutside a patient body to tension the anchors positioned within thebody. Generally, the handle assembly may comprise handle 211 and ahollow elongate shaft 215 extending from the handle 211. Shaft 215 mayfunction much like a laparoscopic shaft if shaft 215 is rigid;alternatively, shaft 215 may be configured to be flexible foradvancement within or through an endoscope or other working lumen, if sodesired. A tensioning assembly, as described above, may be positionedwithin the lumen of shaft 215 near or at the distal end of shaft 215 andthe control mechanisms, e.g., suture coupler 212, may be actuatable fromhandle 211. In one variation, control wheel or ratchet control 213,which may be located on handle 211, may be rotated in the direction ofarrow 217 to actuate base 205 or suture coupler 212 in a proximaldirection, as indicated by arrow 219. Tensioning suture 38 with ratchetcontrol 217 may draw anchors 207, 209 towards one another to securetissue fold F while also applying an appropriate load upon anchors 207,209.

Various other factors of the tissue anchors may be modified to affectthe tensioning and loading characteristics when deflecting the anchors.Moreover, some of the factors may also affect the interaction of theanchor with respect to the tissue in ensuring that the tissue is notover-compressed and that adequate blood flow may occur within the tissuedirectly beneath the anchor.

One factor may include varying the number of arms or struts of theanchor. For instance, the anchor may be configured to have, e.g., sevenstruts or arms 12 which deflect about the proximal 14 and distal 16collars, as shown in the flattened view of one anchor variation 220 inFIG. 15A. FIG. 15B shows a side view of the flattened anchor 220 whileFIG. 15C shows a perspective view of the anchor 220 in an unexpandeddelivery configuration.

FIG. 16A shows another variation of anchor 230 in a flattened view withstruts or arms 232 extending between proximal collar 236 and distalcollar 238. In this variation, five arms 232 may be utilized to increasethe spacing 234 defined between adjacent arms 232. The increased spacing234 may be utilized to ensure the blood flow in the tissue beneath thetissue. FIG. 16B shows a side view of the flattened anchor 230 and FIG.16C shows a perspective view of anchor 230 in its unexpanded deliveryconfiguration. Other variations are discussed below.

Aside from varying the number of struts or arms, the configuration ofthe arms themselves may be varied. As seen in FIG. 16A, cross-sectionsof an individual arm 232 may be viewed for discussion purposes at threesections, proximal I, middle II, and distal III portions of the arm 232.FIGS. 17A to 17J show examples of possible variations forcross-sectional areas of an arm at each section, proximal I, middle II,and distal III. These figures are not intended to be limiting but aremerely intended as examples of possible arm configurations.

FIG. 17A shows an arm configuration where sections I and III may besquare in shape with the middle section II rectangular.

FIG. 17B shows an arm configuration where sections I and III may berectangular in shape with the middle section II square.

FIG. 17C shows an arm configuration where sections I and III may berectangular in shape in a transverse direction with the middle sectionII square.

FIG. 17D shows an arm configuration where sections I and III may besquare in shape with the middle section II rectangular in a traversedirection.

FIG. 17E shows an arm configuration where all sections I, II, and IIImay be square in shape.

FIG. 17F shows an arm configuration where all sections I, II, and IIImay be rectangular in shape.

FIG. 17G shows an arm configuration where sections I and III may becircular in shape with the middle section II rectangular.

FIG. 17H shows an arm configuration where sections I and III may beelliptical in shape with the middle section II circular.

FIG. 17I shows an arm configuration where sections I and III may becircular in shape with the middle section II elliptical.

FIG. 17J shows an arm configuration where all sections I, II, and IIImay be circular in shape.

As mentioned above, varying the number of struts or arms may be utilizedto vary not only the contact area with respect to the underlying tissue,but to also affect the optimal loading characteristics of the anchor.Aside from the number of arms, the positioning of the arms may also beutilized. For example, FIGS. 18A to 18F show end views of anchorvariations having a number of varying arms and arm positions. Again,these figures are not intended to be limiting but are merely intended asexamples.

FIG. 18A shows the end view of an anchor 240 having 3 arms uniformlyspaced apart.

FIG. 18B shows the end view of an anchor 242 having 4 arms uniformlyspaced apart.

FIG. 18C shows the end view of an anchor 244 having 5 arms uniformlyspaced apart.

FIG. 18D shows the end view of an anchor 246 having 6 arms uniformlyspaced apart.

FIG. 18E shows the end view of an anchor 248 having 7 arms uniformlyspaced apart.

FIG. 18F shows the end view of an anchor 250 having 9 arms uniformlyspaced apart.

Any number of arms may be utilized as practicable and although the armsin the above examples are uniformly spaced apart from one another, thespacing between the arms may be varied irregularly or arbitrarilyprovided that the spacing between the arms enable adequate blood flow inthe underlying tissue.

Not only can the number of arms and spacing between the arms be varied,but also the arm configurations themselves. For instance, the arms maybe pre-formed into various shapes depending upon the desired effects onthe anchor loading characteristics. As above, these figures are notintended to be limiting but are merely intended as examples.

FIG. 19A shows an illustrative side view of anchor 260 having curvedarms.

FIG. 19B shows an illustrative side view of anchor 262 havingcircularly-shaped arms.

FIG. 19C shows an illustrative side view of anchor 264 havingelliptically-shaped arms.

FIG. 19D shows an illustrative side view of anchor 266 having bow-shapedarms.

FIG. 19E shows an illustrative side view of anchor 268 having armsshaped into a figure-eight manner.

FIG. 19F shows an illustrative side view of anchor 270 havingminimally-radiused arms.

Aside from the arm shapes, the length of the collars may be varied aswell. FIG. 20A shows anchor variation 280 having extended anchor collars282, which may act to reduce the radius of the arms. FIG. 20B showsanchor variation 284 having reduced collars 286, which may act toincrease the radius of the arms. As above, these figures are notintended to be limiting but are merely intended as examples.

When the anchors are deployed into or against the tissue, at least oneportion of the anchor arms are generally against the tissue surfacewhile another portion of the arms are exposed within the lumen. Theexposed portions of the anchor may be optionally coated or covered witha material to protect against exposure to foreign materials, e.g., foodor other object which may be ingested by the patient, other surgicaltools, etc. Accordingly, as shown in the perspective view of anchorvariation 290 in FIG. 21A, biocompatible coating or covering 292 may beplaced over the entire length of the anchor arms 12 or only along theportions of the arms 12 not against the tissue. The coating or covering292 may be comprised from various materials, e.g., elastomers, plastics,etc.

Alternatively, a mesh or skirt-like covering 298 may be placed over theexposed portion of the anchor 294, as shown in FIG. 21B, which isattached to the anchor via attachment points 298 along each of some ofthe arms 12. Yet another alternative may be seen in anchor variation 300in FIG. 21C in which the entire anchor itself may be covered with adistensible or expandable covering or mesh.

Although a number of illustrative variations are described above, itwill be apparent to those skilled in the art that various changes andmodifications may be made thereto without departing from the scope ofthe invention. Any of the modifications to an anchor, e.g., number ofarms, arm configuration, cross-sectional variations, anchor collarlength, coatings or coverings over the anchor, etc., may be done in avariety of combinations with one another. For instance, depending uponthe desired loading characteristics, an anchor may be made having anumber of arms with various cross-sectional areas along one or more ofthe arm lengths and may additionally have one or both collars varied inlength.

Any of the combinations or modifications is intended to be within thescope of this invention. Moreover, although configurations may be shownwith various types of anchors, it is intended that the variousconfigurations be utilized in various combinations as practicable. It isintended in the appended claims to cover all such changes andmodifications that fall within the true spirit and scope of theinvention.

1.
 1. A system for loading an anchor for placement against a tissuesurface, comprising: an anchor body having a delivery configuration andan expanded configuration adapted for placement against the tissuesurface; and a loading mechanism in communication with the anchor body,wherein the loading mechanism is adapted to indicate a loading conditionupon the anchor body.
 2. The system of claim 1 further comprising alength of suture extending between the anchor body and the loadingmechanism.
 3. The system of claim 2 further comprising a lockingmechanism adapted to pass the anchor body in a first direction relativeto the length of suture upon application of a cinching force.
 4. Thesystem of claim 3 wherein the locking mechanism is further adapted toimpart a locking force upon the length of suture when the anchor body isurged in a second direction opposite to the first direction, and whereinthe locking force is greater than the cinching force.
 5. The system ofclaim 1 wherein the anchor body is adapted to be delivered through ahollow member for placement against the tissue surface.
 6. The system ofclaim 5 wherein the hollow member comprises a needle.
 7. The system ofclaim 1 wherein the anchor body comprises a basket-type anchor.
 8. Thesystem of claim 1 wherein the anchor body comprises a plurality ofreversibly deformable arms extending between a proximal collar and adistal collar.
 9. The system of claim 8 wherein each of the deformablearms are adapted to contact the tissue surface.
 10. The system of claim1 wherein the anchor body comprises a plurality of deformable arms whichare configured to define a space between adjacent arms for minimizingcontact between the anchor body and the tissue surface.
 11. The systemof claim 1 wherein the anchor body is comprised of a shape memory orsuperelastic alloy.
 12. The system of claim 1 wherein the anchor body iscomprised of nitinol.
 13. The system of claim 1 wherein the loadingcondition is indicative of a deformation state of the anchor body. 14.The system of claim 1 wherein the loading mechanism is further adaptedto indicate a predetermined loading condition upon the anchor body. 15.The system of claim 14 wherein the predetermined loading condition isindicative of a deformation range where the anchor body exerts asubstantially constant force upon the tissue surface.
 16. The system ofclaim 1 wherein the loading mechanism comprises a post extending fromthe anchor body, the post being configured to inhibit deformation of theanchor body beyond a predetermined limit.
 17. The system of claim 1wherein the loading mechanism comprises: a first member defining a firstregion with a first frictional coefficient; a second member defining atleast a second region with a second frictional coefficient differentfrom the first frictional coefficient, wherein the first member and thesecond member are adapted to slide relative to one another such that afirst frictional force is generated by contact between the first regionand the second region, and wherein a change in the first frictionalforce is indicative of a predetermined loading condition upon the anchorbody.
 18. The system of claim 17 wherein the second member furtherdefines a third region with a third frictional coefficient differentfrom the second frictional coefficient.
 19. The system of claim 17wherein the first member comprises an elongate tubular member.
 20. Thesystem of claim 17 wherein the second member comprises an outer membercircumferentially disposed over the first member.
 21. The system ofclaim 17 wherein the first member or the second member further comprisesa stop adapted to limit a longitudinal motion between the respectivemembers.
 22. The system of claim 1 wherein the loading mechanismcomprises a spring member having a predetermined spring coefficient. 23.The system of claim 1 wherein the loading mechanism comprises a straingauge adapted to measure a longitudinal deformation of a tensionedregion, the deformation being indicative of the loading condition uponthe anchor body.
 24. The system of claim 23 further comprising a monitorin communication with the strain gauge, the monitor being adapted toindicate a predetermined loading condition upon the anchor.
 25. Thesystem of claim 1 wherein the loading mechanism comprises a stop locatedupon the anchor body, the stop being configured to inhibit deformationof the anchor body beyond a predetermined limit.
 26. The system of claim1 wherein the loading mechanism comprises a fuse member adapted to breakwhen a predetermined loading condition is reached, thereby inhibitingdeformation of the anchor body beyond a predetermined loading condition.27. The system of claim 26 wherein the fuse member comprises a length ofmaterial having a known failure strength.
 28. The system of claim 26wherein the fuse member comprises a notched material.
 29. The system ofclaim 1 further comprising a covering or coating disposed at leastpartially over the anchor body.
 30. A method for loading an anchor forplacement against a tissue surface, comprising: positioning the anchorrelative to the tissue surface; applying a load to the anchor such thatthe anchor is configured into a partially compressed state against thetissue surface; and adjusting the load such that the anchor exerts asubstantially constant force upon the tissue surface.
 31. The method ofclaim 30 wherein positioning the anchor comprises deploying the anchorvia a hollow needle against the tissue surface.
 32. The method of claim30 wherein positioning the anchor comprises configuring the anchor froma delivery configuration to an expanded configuration.
 33. The method ofclaim 30 wherein positioning the anchor comprises deploying a pluralityof deformable arms against the tissue surface such that a space isdefined between adjacent arms for minimizing contact between the anchorand the tissue surface.
 34. The method of claim 30 wherein applying aload to the anchor comprises applying the load to a length of suture.35. The method of claim 34 further comprising imparting a locking forceupon the length of suture such that the locking force inhibits theanchor from relaxing from its compressed state.
 36. The method of claim30 wherein adjusting the load comprises applying a predetermined loadingcondition upon the anchor.
 37. The method of claim 30 wherein adjustingthe load comprises applying the load until the anchor exerts thesubstantially constant force upon the tissue surface over a range ofdeflection of the anchor.
 38. The method of claim 30 wherein adjustingthe load comprises applying the load until a change in the load isdetected.
 39. The method of claim 30 wherein adjusting the loadcomprises detecting the substantially constant force via a spring memberhaving a predetermined spring coefficient.
 40. The method of claim 30wherein adjusting the load comprises detecting the substantiallyconstant force via a strain gauge adapted to measure a longitudinaldeformation of a tensioned region.
 41. The method of claim 30 whereinadjusting the load comprises detecting the substantially constant forcevia a fuse member adapted to break when the constant force is reached.